1. Field of the Invention
This invention relates in general to offshore drilling equipment and in particular to a means for stabilizing a wellhead in a wellhead housing.
2. Description of the Prior Art
In one method of drilling offshore wells with floating vessels, a large diameter hole is first drilled or jetted, then conductor pipe is cemented in the large diameter hole with a wellhead housing at the top. The wellhead housing is supported by a guide structure that rests on the sea floor. A second hole of smaller diameter is then drilled. A first string called surface casing is lowered into this second diameter hole, with a wellhead at the top which is supported by the wellhead housing. A latch secures the wellhead to the wellhead housing to prevent upward movement.
Pressure sealing equipment is mounted to the top of the wellhead. A ball joint connects the pressure equipment to risers which extend to the drilling vessel. Drill pipe is lowered through the risers, pressure equipment, and wellhead for drilling the well to a further depth.
During drilling, the drilling vessel may drift or move laterally with respect to the wellhead. Although the ball joint allows a certain amount of movement, bending forces are exerted on the wellhead. There is an annular space between the wellhead and the wellhead housing that is normally filled with cement when the wellhead is set. This annular space allows some flexing of the wellhead within the wellhead housing. This side-to-side movement can cause fatigue in the casing directly below the wellhead and may result in parting of the casing.